Hybrid drive system

ABSTRACT

A hybrid drive system configured with an input shaft and a friction type continuously variable transmission (CVT) device. The CVT includes an input member drivingly connected to the input shaft, and an output member. Rotation of the input member is steplessly changed in speed and transmitted to the output member by a shear force of an oil film interposed at the contact position. The drive system includes an electric motor having a dedicated output shaft, a differential device, and a gear transmission device that is structured from a meshing rotary transmission mechanism. A case includes at least a first space filled with traction oil and accommodating the CVT device, and a second space filled with lubricant oil and accommodating the gear transmission device.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2009-218120 filed on Sep. 18, 2009, including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a hybrid drive system in which an engine and an electric motor drive a vehicle wheel, and more specifically relates to a hybrid drive system that integratedly incorporates a friction type continuously variable transmission device, such as a cone ring continuously variable transmission device.

DESCRIPTION OF THE RELATED ART

A conventional hybrid drive system in which an engine and an electric motor drive a vehicle wheel is known that integratedly incorporates one electric motor and a continuously variable transmission device. A belt type continuously variable transmission device is generally used as the continuously variable transmission device for the hybrid drive system. The belt type continuously variable transmission device is formed from a pair of pulleys and a belt (or chain) made of metal that is wound around the pulleys, and steplessly changes the speed by changing an effective diameter of the pulleys.

Also known is a cone ring type continuously variable transmission device that is formed from a pair of conical friction wheels and a ring made of metal interposed between the friction wheels. By moving the ring so as to change contacting portions between the ring and the friction wheels, the speed is steplessly changed (see Published Japanese Translation of PCT Application No. 2006-501425 (JP2006-501425A), for example).

SUMMARY OF THE INVENTION

In the conventional hybrid drive system, the electric motor is arranged coaxial to an output shaft of the engine, and the belt type continuously variable transmission device and a gear transmission device formed from a plurality of gears are both housed inside the same case and lubricated by the same lubricant oil, e.g. ATF or the like.

The cone ring type continuously variable transmission device may also be applied as a continuously variable transmission device for the above hybrid drive system. In such case, the belt type continuously variable transmission device can achieve a desired transmission torque even in the presence of lubricant oil, and the contact surface area between the pulleys and the metal belt is relatively broad; however, the contact surface area between the conical friction wheels and the metal ring is small and it is difficult to achieve a desired transmission torque with lubricant oil, so the use of specialized traction oil for achieving a sufficient shear torque is preferable.

The belt type continuously variable transmission device also has a relatively small axial dimension and the electric motor can be arranged coaxial to the output shaft of the engine. However, the friction type, that is, the cone ring type, continuously variable transmission device is relatively long in the axial direction. Therefore, the overall layout of the hybrid drive system, including the arrangement of the electric motor, must be improved due to restrictions in terms of automobile installation.

The present invention provides a hybrid drive system wherein a friction type, that is, a cone ring type, continuously variable transmission device is accommodated in an enclosed space defined from a space that accommodates a gear transmission device and the enclosed space is filled with traction oil, such that reliable torque transmission and shifting can be achieved in a compact structure.

The present invention is a hybrid drive system that includes: an input shaft that moves in accordance with an engine; a friction type continuously variable transmission device that includes an input member that is drivingly connected to the input shaft, and an output member, wherein a contact position between the input member and the output member is changed, and a rotation of the input member is steplessly changed in speed and transmitted to the output member by a shear force of an oil film interposed at the contact position; an electric motor that includes a dedicated output shaft; a differential device; a gear transmission device that forms at least part of a power transmission path that transmits a rotation of the output shaft of the electric motor to the differential device, and is structured from a meshing rotary transmission mechanism; and a case that includes at least a first space that is filled with traction oil and accommodates the friction type continuously variable transmission device, and a second space that is filled with lubricant oil and accommodates the gear transmission device, wherein the first space and the second space are divided in an oil-tight manner.

Note that, in the present invention, the term “gear” refers to a meshing rotary transmission mechanism including toothed gears and sprockets. Thus, the gear transmission device refers to a transmission device that uses the meshing transmission mechanism. Further note that the dedicated output shaft of the electric motor refers to a shaft that is different from the input shaft, the input member and the output member of the continuously variable transmission device, and shafts of the differential device.

The output shaft of the electric motor is a first shaft. The input shaft and the input member of the friction type continuously variable transmission device disposed coaxially form a second shaft. The output member of the friction type continuously variable transmission device is a third shaft. Right and left axle shafts connected to the differential device form a fourth shaft. The first, second, third, and fourth shafts are arranged mutually parallel and rotatably supported by the case, and gears that form the gear transmission device are disposed on the first, second, third, and fourth shafts. The electric motor and the continuously variable transmission device are disposed on a first side in an axial direction of the gear transmission device, and a second side of the gear transmission device is connected to the engine.

The gear transmission device transmits a rotation of the output shaft of the electric motor to the input member of the friction type continuously variable transmission device, and transmits a rotation of the output member to the differential device.

The case includes: a first case member that supports a first end portion of the output shaft of the electric motor, respective first end portions of the input member and the output member of the friction type continuously variable transmission device, and a first end portion of a differential case of the differential device; a second case member that supports a second end portion of the output shaft of the electric motor, the input shaft, an output shaft mounted with the output member of the friction type continuously variable transmission device, and a second end portion of the differential case of the differential device; and a partition that supports respective second end portions of the input member and the output member of the friction type continuously variable transmission device, wherein the first case member and the second case member are connected, and the partition divides the first space and the second space in an oil-tight manner.

The gear transmission device includes an output gear that is provided on the output shaft of the electric motor, and a differential ring gear that forms an input portion of the differential device, wherein the output gear and the differential ring gear disposed so as to overlap in the axial direction.

The gear transmission device includes an intermediate gear that is provided on the input shaft and moves in accordance with the output gear, and an output gear of the continuously variable transmission device that is provided integrated with the output member of the friction type continuously variable transmission device in a rotating direction, wherein the intermediate gear and the output gear of the continuously variable transmission device are disposed so as to overlap the output gear and the differential ring gear in the axial direction.

Referring to FIG. 1, for example, the output gear and the intermediate gear are toothed gears, and power is transmitted between the toothed gears through a toothed idler gear.

Referring to FIG. 3, for example, the output gear and the intermediate gear are sprockets, and power is transmitted between the sprockets through a chain wound between the sprockets.

The toothed idler gear is disposed overlapping the electric motor in a radial direction.

The friction type continuously variable transmission device is a cone ring type continuously variable transmission device, with the input member and the output member formed from conical friction wheels that are disposed such that axes of the friction wheels are mutually parallel and large diameter portions and small diameter portions of the friction wheels are respectively opposite each other in the axial direction, and a ring provided interposed between opposing inclined surfaces of the friction wheels and moved in the axial direction to steplessly change a speed.

The input shaft and the input member of the friction type continuously variable transmission device are drivingly connected by a spline.

According to a first aspect of the present invention, a case includes a first space that is filled with traction oil and a second space that is filled with lubricant oil, which are defined in an oil-tight manner. In addition, a friction type continuously variable, transmission device is housed in the first space, and a gear transmission device is housed in the second space. Therefore, an oil film of the traction oil, which has a large shear force particularly in an extreme pressure condition, is present on contact positions of the friction type continuously variable transmission device, and torque is transmitted by the shear force. A desired torque can thus be transmitted without early wear occurring on friction transmission members such as an input member and an output member, and swift and smooth shifting achieved. Further, the gear transmission device can achieve smooth power transmission with high transmission efficiency in the presence of the lubricant oil without generating a large power loss.

Accordingly, the present invention is a hybrid drive system capable of handling a large shift region spanning from start off to high speeds and large torque fluctuations including acceleration, deceleration, and slope roads. Power from an electric motor is transmitted with high efficiency to a differential device, and a rotation of an engine is steplessly changed in speed in a swift and smooth manner and then transmitted to the differential device. A control is performed such that the electric motor appropriately assists while the engine achieves a swift and suitable output. It is thus possible to provide a hybrid drive system that enables a sufficient fuel economy improvement and carbon dioxide reduction effect with a relatively inexpensive configuration that uses a friction type continuously variable transmission device having a simple constitution.

According to a second aspect of the present invention, an input shaft that moves in accordance with the engine is disposed coaxial with an input shaft of the continuously variable transmission device, and the electric motor is disposed on a first shaft different from a second shaft, whereby installation space for the electric motor can be secured and the electric motor can be employed with space remaining in the axial direction. In addition, gears of the gear transmission device are respectively disposed on the shafts. The electric motor and the continuously variable transmission device are disposed on a first side in the axial direction of the gear transmission device, and a second side of the gear transmission device is connected to the engine. Therefore, the overall layout of the hybrid drive system can be made compact and mounted in a vehicle, even a small passenger vehicle with strict space restrictions, while also using the friction type continuously variable transmission device that is relatively long in the axial direction.

According to a third aspect of the present invention, a rotation of the electric motor is transmitted to the differential device through the continuously variable transmission device. Therefore, a lower capacity electric motor can be used.

According to fourth aspect of the present invention, the case is formed by combining (dividing the case into) a first case member and a second case member. A partition defines the first space and the second space in an oil-tight manner. Therefore, the shafts of the friction type continuously variable transmission device and the like, which are subject to a relatively large thrust force, are suitably supported, a case that surely defines the first and second spaces in an oil-tight manner can be obtained with a robust and compact configuration.

According to a fifth aspect of the present invention, an output gear of the electric motor and a differential ring gear are disposed so as to overlap in the axial direction. According to a sixth aspect of the present invention, an intermediate gear and an output gear of the continuously variable transmission device are also disposed so as to overlap in the axial direction. Therefore, the gear transmission device can be made more compact, particularly in the axial direction. Thus, the overall hybrid drive system can be made more compact, and the second space can be narrowed (reduced in capacity) so as to decrease the amount of lubricant oil filling the second space. At the same time, oil can be surely scooped up by the differential ring gear and lubricant oil can be reliably supplied to the other overlapping gears.

According to a seventh aspect of the present invention, a toothed idler gear is provided. Therefore, a toothed gear with a small diameter such as a pinion can be used for the motor output gear, which increases a reduction ratio with the intermediate gear and enables the use of a low-capacity, small electric motor. Thus, the hybrid drive system can be made even more compact.

According to an eighth aspect of the present invention, sprockets are used for the motor output gear and the intermediate gear, and the rotation of the electric motor is transmitted through a chain. Therefore, the degree of design freedom regarding an inter-axial distance among the electric motor, the input shaft, and the input member of the continuously variable transmission device can be increased.

According to a ninth aspect of the present invention, the toothed idler gear is disposed so as to overlap the electric motor in a radial direction. Therefore, the input member of the continuously variable transmission device and the electric motor can be disposed closer together without interfering with a shaft-supporting portion of a partition of an idler shaft. Thus, the hybrid drive system can be made even more compact.

According to a tenth aspect of the present invention, the friction type continuously variable transmission device is a cone ring type continuously variable transmission device formed of two conical friction wheels and a ring. Therefore, a desired gear ratio can be obtained in a prescribed space (dimension), and the traction oil effectively functions at friction contact-separation positions in an extreme pressure condition. In addition, an input-side friction wheel and an output-side friction wheel are disposed mutually parallel, and shafts (a second shaft and a third shaft) thereof are mounted with gears to configure the gear transmission device compact. By narrowing the width of the second space, it is possible to use the cone ring type continuously variable transmission device that is relatively long in the axial direction, and an overall sensible hybrid drive system can be achieved.

According to an eleventh aspect of the present invention, vibrations of the input shaft that moves in accordance with the engine are absorbed by a spline and not transmitted to the input member of the continuously variable transmission device, so that the input member can be supported with high precision. Thus, a friction type continuously variable transmission device that applies a large contact pressure with high precision to contact positions to transmit engine power can be used in the hybrid drive system, while also achieving smooth and reliable power transmission and shifting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front cross-sectional view that shows a hybrid drive system to which the present invention is applied;

FIG. 2 is a side view of the hybrid drive system; and

FIG. 3 is a front cross-sectional view that shows a hybrid drive system according to a partially modified embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A hybrid drive system to which the present invention is applied will be described below with reference to the attached drawings. As shown in FIGS. 1 and 2, a hybrid drive system 1 includes an electric motor 2, a cone ring type continuously variable transmission device (a friction type continuously variable transmission device) 3, a differential device 5, an input shaft 6 that moves in accordance with an output shaft of an engine (not shown), and a gear transmission device 7. The above devices and shafts are housed in a case 11 that is formed by two case members, that is, a case member 9 and a case member 10. Further, the case 11 includes a first space A and a second space B divided by a partition 12 in an oil-tight manner.

The electric motor 2 includes a stator 2 a fixed to the first case member 9, and a rotor 2 b provided on an output shaft 4. A first end portion of the output shaft 4 is rotatably supported by the first case member 9 through a bearing 13, and a second end portion of the output shaft 4 is rotatably supported by the second case member 10 through a bearing 15. An output gear 16 consisting of a toothed gear (pinion) is formed on a second side of the output shaft 4, and meshes with an intermediate gear (toothed gear) 19 provided on the input shaft 6 through a toothed idler gear 17.

A shaft 17 a of the toothed idler gear 17 includes a first end portion that is rotatably supported by the partition 12 through a bearing 20, and a second end portion that is rotatably supported by the second case member 10 through a bearing 21. The toothed idler gear 17 is disposed partially overlapping with the electric motor 2 in a radial direction when viewed from the side (that is, when viewed in an axial direction). Specifically, the output gear 16 consisting of a pinion has a small diameter and the intermediate gear 19 of the input shaft 6 has a large diameter, which increases the gear ratio transmitted from the output gear (toothed gear) 16 to the intermediate gear 19 via the toothed idler gear 17 (obtains a large reduction ratio). In addition, the bearing 20 that supports the first end portion of the toothed idler gear shaft 17 a can be disposed closer to the output shaft 2 a of the electric motor 2. Thus, the cone ring type continuously variable transmission device 3 can be disposed closer to the electric motor 2 without a bearing support portion of the partition 12 interfering with a support portion of the continuously variable transmission device 3.

The cone ring type continuously variable transmission device 3 includes a conical friction wheel 22 serving as an input member, a conical friction wheel 23 serving as an output member, and a ring 25 made of metal. The friction wheels 22, 23 are disposed so as to be mutually parallel, and a small diameter portion and a large diameter portion of the friction wheel 22 is disposed axially opposite to a small diameter portion and a large diameter portion of the friction wheel 23. The ring 25 is interposed between opposing inclined surfaces of the friction wheels 22, 23 and surrounds one of the friction wheels, for example, the input-side friction wheel 22. A large thrust force acts on at least one of the friction wheels, and therefore the ring 25 is interposed between the inclined surfaces by a relatively large clamping force based on this thrust force. Specifically, a cam mechanism is formed between the output-side friction wheel 23 and an output shaft 23 a on surfaces opposed to each other in the axial direction. The thrust force in a direction shown by an arrow D in the drawing is generated in accordance with the transferred torque, and a large clamping force is generated to act on the ring 25 between the output-side friction wheel 23 and the input-side friction wheel 22 that is supported in a direction that counters the thrust force.

The input-side friction wheel 22 includes a first end portion (large diameter portion side) supported by the first case member 9 through a roller bearing 26, and a second end portion (small diameter portion side) supported by the partition 12 through a tapered roller bearing 27. The output-side friction wheel 23 includes a first end portion (small diameter portion side) supported by the first case member 9 through a roller bearing 29, and a second end portion (large diameter portion side) supported by the partition 12 through a roller (radial) bearing 30. The output shaft 23 a, which applies to the output-side friction wheel 23 the thrust force acting in the direction shown by the arrow D as described above, includes a second end supported by the second case member 10 through a tapered roller bearing 31. An inner race of the bearing 27 is interposed between a stepped portion and a nut 32 on the second end portion of the input-side friction wheel 22, and the thrust force that acts on the input-side friction wheel 22 through the ring 25 in the direction shown by the arrow D from the output-side friction wheel 23 is supported by the tapered roller bearing 27. On the other hand, a reaction force of the thrust force acting on the output-side friction wheel 23 acts on the output shaft 23 a in a direction opposite to the direction shown by the arrow D, and the reaction force of the thrust force is supported by the tapered roller bearing 31.

The ring 25 moves in the axial direction by an axial moving mechanism, such as a ball screw, and changes the positions of contact between the ring 25 and the input-side friction wheel 22 and between the ring 25 and the output-side friction wheel 23, so as to steplessly change the speed by steplessly changing a rotation ratio between the input member 22 and the output member 23. The reaction force and the thrust force D corresponding to the transferred torque are canceled out by the tapered roller bearings 27, 31 in the integrated case 11, and an equilibrant force such as a hydraulic pressure is not required.

The differential device 5 includes a differential case 33, and the differential case 33 includes a first end portion supported by the first case member 9 through a bearing 35, and a second end portion supported by the second case member 10 through a bearing 36. A shaft that is perpendicular to the axial direction is attached to the inside of the differential case 33, and bevel gears 37, 37, which serve as differential carriers, are engaged with the shaft. Left and right axle shafts 39 l, 39 r are supported by the shaft, and bevel gears 40, 40 that mesh with the differential carriers are fixed to the axle shafts. Further, a differential ring gear (toothed gear) 41 having a large diameter is attached to the outside of the differential case 33.

The output shaft 23 a of the continuously variable transmission device is formed with a toothed gear (pinion) 44, and the toothed gear 44 meshes with the differential ring gear 41. The motor output gear (pinion) 16, the toothed idler gear 17, the intermediate gear (toothed gear) 19, the output gear (pinion) 44 of the continuously variable transmission device, and the differential ring gear (toothed gear) 41 constitute the gear transmission device 7. The motor output gear 16 and the differential ring gear 41 are disposed overlapping each other in the axial direction, and the intermediate gear 19 and the output gear 44 of the continuously variable transmission device are disposed overlapping the motor output gear 16 and the differential ring gear in the axial direction. Note that, a gear 45, which is engaged with the output shaft 23 a of the continuously variable transmission device through a spline, is a parking gear that locks the output shaft when a shift lever is in a parking position. Further, the term “gear” refers to a meshing rotary transmission mechanism including toothed gears and sprockets. In this embodiment, however, the gear transmission device refers to a toothed gear transmission device that is formed by toothed gears only.

The input shaft 6 includes a first end that is engaged (drivingly connected) with the input member 22 of the continuously variable transmission device 3 through a spline S, and a second end side of the input shaft 6 is linked with the output shaft of the engine through a clutch (not shown) housed in a third space C defined by the second case member 10, so that the input shaft 6 moves in accordance with the output shaft of the engine. The second case member 10 is open and connected to the engine (not shown) on a third space C side.

The gear transmission device 7 is housed in the second space B. The second space B is a space between the third space C, and the electric motor 2 and the first space A, in the axial direction. The second space B is defined by the second case member 10 and the partition 12. The shaft-supporting portions (27, 30) of the partition 12 are placed in an oil-tight state by oil seals 47, 49, respectively, and the shaft-supporting portions of the second case member 10 and the first case member 9 are shaft-sealed by oil seals 50, 51, 52. The second space B is configured to be oil-tight, and is filled with a predetermined amount of a lubricant oil such as ATF. The first space A defined by the first case member 9 and the partition 12 is similarly configured to be oil-tight, and is filled with a predetermined amount of a traction oil having a shear force, and a large shear force under an extreme pressure condition in particular.

Referring to FIG. 2, the output shaft 4 of the electric motor 2 is a first shaft I; the coaxially disposed input shaft 6 and the input member 22 of the continuously variable transmission device form a second shaft II; the output member 23 of the continuously variable transmission device and the output shaft 23 a thereof form a third shaft III; the left and right axle shafts 39 l, 39 r form a fourth shaft IV; and the toothed idler gear shaft 17 a is a fifth shaft V. These shafts are all arranged parallel and supported by the case 11, and the gears (toothed gears) 16, 17, 19, 44, 41 of the gear transmission device 7 are disposed thereon. The electric motor 2 and the continuously variable transmission device 3 are disposed on a first side in the axial direction of the gear transmission device 7, and a second side of the gear transmission device 7 is connected to the engine. Further, the electric motor 2 and the coaxial first shaft I are positioned the highest, while the differential device 5 and the coaxial fourth shaft IV are positioned the lowest. A portion of the ring gear 41 of the differential device 5 lies within the lubricant oil pooled inside the second space B.

Next, the operation of the hybrid drive system 1 as described above will be explained. The hybrid drive system 1 is connected to an internal combustion engine on the third space C side of the case 11, and the output shaft of the engine is connected to the input shaft 6 through a clutch. The power from the engine is transmitted to the input shaft 6, and the rotation of the input shaft 6 is transmitted to the input-side friction wheel 22 in the cone ring type continuously variable transmission device 3 through the spline S. The power is further transmitted to the output-side friction wheel 23 through the ring 25.

During this transmission, a large contact pressure acts between the friction wheels 22, 23 and the ring 25 due to the thrust force acting on the output-side friction wheel 23 in the direction shown by the arrow D. Because the first space A is filled with the traction oil, an oil film of the traction oil is formed between the friction wheels and the ring, bringing about the extreme pressure condition. In this condition, the traction oil has a large shear force, and thus the power is transmitted between the friction wheels and the ring by the shear force of the oil film. This allows the transfer of a predetermined torque in a non-slip manner without causing wear on the friction wheels and the ring, even though the torque transfer is made through contact between metal members. Moreover, the ring 25 moves in the axial direction smoothly to change the positions of contact between both friction wheels and the ring, whereby the speed is steplessly changed.

The rotation of the output-side friction wheel 23 whose speed has been steplessly changed is transmitted to the differential case 33 of the differential device 5 through the output shaft 23 a, the output gear 44, and the differential ring gear 41. The power is then distributed to the left and right axle shafts 39 l, 39 r so as to drive the vehicle wheels (front wheels).

On the other hand, the power from the electric motor 2 is transmitted to the input shaft 6 through the output gear 16, the toothed idler gear 17, and the intermediate gear 19. Similar to the description above, the speed of the rotation of the input shaft 6 is steplessly changed by the cone ring type continuously variable transmission device 3, and the rotation is transmitted to the differential device 5 through the output gear 44 and the differential ring gear 41. The gear transmission device 7 formed by the gears 16, 17, 19, 44, 41, 37, 40 is housed in the second space B filled with the lubricant oil, and therefore the power is smoothly transmitted through the lubricant oil when the gears mesh. At such time, because the differential ring gear 41 (see FIG. 2) disposed at a lower position in the second space B is formed of a large diameter gear, the differential ring gear 41 scoops up the lubricant oil so that a sufficient amount of lubricant oil is reliably supplied to the other gears (toothed gears) 16, 17, 19, 44.

Various operation modes of the engine and the electric motor, that is, operation modes as the hybrid drive system 1, may be employed as necessary. As an example, when the vehicle starts off, the clutch is disconnected and the engine stopped so that the vehicle is started using only the torque from the electric motor 2. Once the vehicle speed reaches a predetermined speed, the engine is started and the vehicle is accelerated by the power from the engine and the electric motor. When the vehicle speed becomes a cruising speed, the electric motor goes into free rotation or is placed in a regeneration mode, and the vehicle travels using only the power from the engine. During deceleration or braking, the electric motor regenerates to charge a battery. Further, the vehicle may be started by the power from the engine using the clutch as a starting clutch, with the torque from the motor used as an assisting power.

The electric motor 2 is disposed on the first shaft, which is different from the second shaft II formed of the input shaft 6 and the like, and also disposed at a position that axially overlaps with the continuously variable transmission device 3. In addition, the gear transmission device 7 is disposed in a relatively narrow space among the continuously variable transmission device 3, the electric motor 2, and the engine. Accordingly, even if the continuously variable transmission device is a friction wheel type continuously variable transmission device that requires relative space in the axial direction, such as the cone ring type continuously variable transmission device, the hybrid drive system 1 can be made compact overall and mounted even in the relatively narrow installation space of a small passenger vehicle or the like, for example. The gears 16, 17, 19, 44, 41 in particular overlap in the axial direction and match the arrangement of the electric motor 2, which reduces the axial dimension. Further, the toothed idler gear 17 overlaps the electric motor 2 in the radial direction. Thus, the electric motor and the continuously variable transmission device can be adjacently arranged to achieve a configuration with a reduced radial dimension.

The toothed idler gear 17 is interposed between the motor output gear 16 and the intermediate gear 19, which enables power transmission at a large reduction ratio from the output gear 16 to the intermediate gear 19. A required torque can thus be obtained using the small motor 2, which contributes to a more compact configuration and a reduction in cost.

Next, a partially modified embodiment will be explained with reference to FIG. 3. Note that the present embodiment differs only with regard to a form of transmission from the motor output gear to the intermediate gear, and other portions are identical to the previous embodiment. Like reference numerals are used for like portions and will not be described again here. In the present embodiment, a motor output gear 16′ and an intermediate gear 19′ are formed of sprockets, and a silent chain 17′ is wound between the sprockets 16′, 19′. The output gear 16′ is in spline engagement with the motor output shaft 4.

Therefore, the rotation of the electric motor 2 is transmitted to the input shaft 6 through the output gear 16′ formed of a sprocket, the silent chain 17′, and the intermediate gear 19′ formed of a sprocket. Note that, in place of the silent chain, another chain such as a roller chain may be used. In the present embodiment, the toothed idler gear used in the previous embodiment is not required, and the shaft-supporting structure is correspondingly simplified (the fifth shaft V is omitted). There is an increased degree of layout design freedom regarding the electric motor 2 and the continuously variable transmission device 3 (especially the input member 22), which is limited only by the extent to which the diameter of the output gear sprocket 16′ can be reduced.

A friction type, that is, a cone ring type, continuously variable transmission device is used as the continuously variable transmission device in the embodiments described above. However, the present invention is not limited to this, and another friction type continuously variable transmission devices may be used, including: a (ring cone type) continuously variable transmission device that disposes a ring so as to encircle two conical friction wheels; a continuously variable transmission device that interposes a friction wheel between two conical friction wheels such that the friction wheel contacts both friction wheels and moves in the axial direction; a continuously variable transmission device that uses a friction wheel with a spherical shape such as a toroidal shape; and a continuously variable transmission device that is provided with pulley-shaped friction wheels of which each is formed of a pair of sheaves that biases input-side and output-side friction discs toward each other so as to sandwich a belt, wherein the pulley-shaped friction wheels move so as to change an inter-axial distance between the friction discs.

The transmission path of the gear transmission device is formed so as to pass through the continuously variable transmission device. However, the transmission path is not limited to this, and the rotation of the electric motor may be transmitted to the differential ring gear 41 without passing through the continuously variable transmission device. In such case, the intermediate gear 19 is rotatably supported by the input shaft 6, and the rotation of the intermediate gear is directly transmitted or transmitted through the idler gear to the output shaft 23 a of the continuously variable transmission device.

The present invention relates to a hybrid drive system that incorporates an electric motor and a friction type continuously variable transmission device such as a cone ring continuously variable transmission device, and is utilized installed in an automobile. 

1. A hybrid drive system comprising: an input shaft that moves in accordance with an engine; a friction type continuously variable transmission device that includes an input member that is drivingly connected to the input shaft, and an output member, wherein a contact position between the input member and the output member is changed, and a rotation of the input member is steplessly changed in speed and transmitted to the output member by a shear force of an oil film interposed at the contact position; an electric motor that includes a dedicated output shaft; a differential device; a gear transmission device that forms at least part of a power transmission path that transmits a rotation of the output shaft of the electric motor to the differential device, and is structured from a meshing rotary transmission mechanism; and a case that includes at least a first space that is filled with traction oil and accommodates the friction type continuously variable transmission device, and a second space that is filled with lubricant oil and accommodates the gear transmission device, wherein the first space and the second space are divided in an oil-tight manner.
 2. The hybrid drive system according to claim 1, wherein the output shaft of the electric motor is a first shaft, the input shaft and the input member of the friction type continuously variable transmission device disposed coaxially form a second shaft, the output member of the friction type continuously variable transmission device is a third shaft, right and left axle shafts connected to the differential device form a fourth shaft, the first, second, third, and fourth shafts are arranged mutually parallel and rotatably supported by the case, and gears that form the gear transmission device are disposed on the first, second, third, and fourth shafts, and the electric motor and the continuously variable transmission device are disposed on a first side in an axial direction of the gear transmission device, and a second side of the gear transmission device is connected to the engine.
 3. The hybrid drive system according to claim 1, wherein the gear transmission device transmits a rotation of the output shaft of the electric motor to the input member of the friction type continuously variable transmission device, and transmits a rotation of the output member to the differential device.
 4. The hybrid drive system according to claim 1, wherein the case includes: a first case member that supports a first end portion of the output shaft of the electric motor, respective first end portions of the input member and the output member of the friction type continuously variable transmission device, and a first end portion of a differential case of the differential device; a second case member that supports a second end portion of the output shaft of the electric motor, the input shaft, an output shaft mounted with the output member of the friction type continuously variable transmission device, and a second end portion of the differential case of the differential device; and a partition that supports respective second end portions of the input member and the output member of the friction type continuously variable transmission device, wherein the first case member and the second case member are connected, and the partition divides the first space and the second space in an oil-tight manner.
 5. The hybrid drive system according to claim 1, wherein the gear transmission device includes an output gear that is provided on the output shaft of the electric motor, and a differential ring gear that forms an input portion of the differential device, wherein the output gear and the differential ring gear disposed so as to overlap in the axial direction.
 6. The hybrid drive system according to claim 5, wherein the gear transmission device includes an intermediate gear that is provided on the input shaft and moves in accordance with the output gear, and an output gear of the continuously variable transmission device that is provided integrated with the output member of the friction type continuously variable transmission device in a rotating direction, wherein the intermediate gear and the output gear of the continuously variable transmission device are disposed so as to overlap the output gear and the differential ring gear in the axial direction.
 7. The hybrid drive system according to claim 6, wherein the output gear and the intermediate gear are toothed gears, and power is transmitted between the toothed gears through a toothed idler gear.
 8. The hybrid drive system according to claim 6, wherein the output gear and the intermediate gear are sprockets, and power is transmitted between the sprockets through a chain wound between the sprockets.
 9. The hybrid drive system according to claim 7, wherein the toothed idler gear is disposed overlapping the electric motor in a radial direction.
 10. The hybrid drive system according to claim 1, wherein the friction type continuously variable transmission device is a cone ring type continuously variable transmission device, with the input member and the output member formed from conical friction wheels that are disposed such that axes of the friction wheels are mutually parallel and large diameter portions and small diameter portions of the friction wheels are respectively opposite each other in the axial direction, and a ring provided interposed between opposing inclined surfaces of the friction wheels and moved in the axial direction to steplessly change a speed.
 11. The hybrid drive system according to claim 1, wherein the input shaft and the input member of the friction type continuously variable transmission device are drivingly connected by a spline.
 12. The hybrid drive system according to claim 2, wherein the gear transmission device transmits a rotation of the output shaft of the electric motor to the input member of the friction type continuously variable transmission device, and transmits a rotation of the output member to the differential device.
 13. The hybrid drive system according to claim 12, wherein the case includes: a first case member that supports a first end portion of the output shaft of the electric motor, respective first end portions of the input member and the output member of the friction type continuously variable transmission device, and a first end portion of a differential case of the differential device; a second case member that supports a second end portion of the output shaft of the electric motor, the input shaft, an output shaft mounted with the output member of the friction type continuously variable transmission device, and a second end portion of the differential case of the differential device; and a partition that supports respective second end portions of the input member and the output member of the friction type continuously variable transmission device, wherein the first case member and the second case member are connected, and the partition divides the first space and the second space in an oil-tight manner.
 14. The hybrid drive system according to claim 13, wherein the gear transmission device includes an output gear that is provided on the output shaft of the electric motor, and a differential ring gear that forms an input portion of the differential device, wherein the output gear and the differential ring gear disposed so as to overlap in the axial direction.
 15. The hybrid drive system according to claim 14, wherein the gear transmission device includes an intermediate gear that is provided on the input shaft and moves in accordance with the output gear, and an output gear of the continuously variable transmission device that is provided integrated with the output member of the friction type continuously variable transmission device in a rotating direction, wherein the intermediate gear and the output gear of the continuously variable transmission device are disposed so as to overlap the output gear and the differential ring gear in the axial direction.
 16. The hybrid drive system according to claim 15, wherein the output gear and the intermediate gear are toothed gears, and power is transmitted between the toothed gears through a toothed idler gear.
 17. The hybrid drive system according to claim 15, wherein the output gear and the intermediate gear are sprockets, and power is transmitted between the sprockets through a chain wound between the sprockets.
 18. The hybrid drive system according to claim 16, wherein the toothed idler gear is disposed overlapping the electric motor in a radial direction.
 19. The hybrid drive system according to claim 18, wherein the friction type continuously variable transmission device is a cone ring type continuously variable transmission device, with the input member and the output member formed from conical friction wheels that are disposed such that axes of the friction wheels are mutually parallel and large diameter portions and small diameter portions of the friction wheels are respectively opposite each other in the axial direction, and a ring provided interposed between opposing inclined surfaces of the friction wheels and moved in the axial direction to steplessly change a speed.
 20. The hybrid drive system according to claim 19, wherein the input shaft and the input member of the friction type continuously variable transmission device are drivingly connected by a spline. 